Eidophor liquid regenerating system



Jan. 1, 1957 J, R ARM 2,776,339

EIDOPHOR LIQUID REGENERATING SYSTEM Filed Sept. 5, 1953 2 Sheets-Sheet l IN V EN TOR:-

(4, WW gm, Qlgf I.

Jan. 1, 1957 J. R. ARNl 5 3 EIDOPHOR LIQUID REGENERATING SYSTEM Filed Sept. 3, 1955 2 Sheets-Sheet 2 INVENTORi- All United States Patent nmornon noon REGENERATINGLSYSTEM JohannRudolf. Ami, Geneva, Switzerland, assignor to Edgar Gretener, Zurich, Switzerland Application September 3, 1953; Serial No; 3785329 Claims priority, application Switzerland September 5,1952

The present, invention relatesto television projection apparatus.

Television projection apparatus have become known, wherein the light flux produced by a separate lig'h'tsourc'e is. controlled point by point by means ofa liquid which adheres to the surface of a rotating support in a=thin layer andwhich for the purpose of light control' is infliienced point by point in accordance with theimage content by' a cathode-ray. Such apparatus as have been described in United States Patents No. 2,740,829 and No 2,740,830 (patent applications of Edgar Gretener Serial No. 245,023 and No. 245,024) employ a -con'cave reflector as support which forms part of a-Schli'erenopticalx'system"servingfor lighticontrol. In cases of -reproduction-Jot colored orstereoscopic imagessone come mon 'or several separate concave reflectors 1may1 alternatively be employed as support.

In order to achieve the desired; control: effect; the liquid serving as control medium mustcshave hi'ghiinternal friction.andaverylow; but exactly;definedr;electrical conductivity. It hasbeen shownr thatra:certainr fatigue? ofsthe control: liquidtitakes placedriring-projectionzwln'rih is' probablyt-due to alterations 'ofthevelectricakpropr ertiess. If the-liquid ispermitted to rest for -ascertain time,:.this alteration disappears torveryhigh-extents- "thoughenot entirely: the-liquid regenerates and maybe usedaiagainz Means hitherto employed.-ion-exchanging the econtroldliquidon thesupport provedpunsatisfactorxy Theuliquid is highly viscous and-sticksfast, to--the sup; port .SO that it: is very-difl"1cult to-remove-gtheboundary layer: next tovthe-r surface ofthe. support. I This however-,1 is-necessary was only a complete removal .ofthe. con: trol. :liquid; will permitregeneration thereof and thus guarantees a periodofoperation satisfactory ion-practical employment-.:

The inventiomis to overcome these disadvantagesa. It is..related to. such television projectionapparatus; wherein a' light -flux.-produced. by aseparatev light source is ;con.- trolled: point by point. by the aid of a liquid which adheres: to the surface. of :the rotating support inatthin layer-.andiwhich', forthev purpose. of effecting .a-..light con.- trol... actionis. influencedpoint, by pointcin. accordance with thesimage content by a...cathode.ray.when passing through. :an. image field.. Accordingto the. invention it is tcharacterized-by-a fluid .circuitdriven. by. a pump, whereinthe. usedaliquid layer: adhering. to thesupport afiter passing. through: the image field..is. replaced.by.a newlayerof liquid by means of. aslit-shapedscavenging nozzle,v and wherein the removed, usedliquiddsragain fed to :the scavenging-nozzle through a storage? tank..of sufficient size.

The invention will. now. beexplainedin. detailain the following .withcthe; aid .of the. embodiments. represented inthe. attached drawings...

Fig.,.1 in perspective schematic representation: shows a televisionprojection apparatus providing a liquidfcircuit according to the present invention, and

Fig. 2' a section of the scavenging nozzle employed in the embodiment of Fig. 1.

Fig. 3; shows as further embodiment a particular construction of the concave reflector by such a television projection apparatus.

Fig. 1 shows a television projection apparatus in schematic perspective representation as an embodiment of the present invention. It comprises a concave reflector 1, a bar system 2, a projection lens 3, a cathode ray tube 4' and. a light source 5, by way of example an arc lamp. The surface directed towards the light source of the bars of bar system 2 is made reflecting. The bar system is consequently also referred to as mirror bar system. A control medium 6, by way of. example a liquidof high internal friction, is spread over the concave reflector 1 in a thin layer. The cathode ray 7 generated by the cathode ray tube 4 is led across the rectangular image field 9 on contiguous lines S'by deflection means'not shown. The cathode ray is modulated in a suitable. manner by the incoming television signals and producesfinely rastered surface deformations within the rectangular image field, which are proportional point by point to. the gradation of brightness of the image to, be reproduced. The center of symmetry 10 of mirror bar system 2 is located at the center of curvature of concave mirror 1' so that the mirror bar system is imaged upon itself. by thev latter. An illumination system, according to representation. a concave mirror 11, directs the light produced by light source 5 towards the bar system 2. By the reflecting surface 12' of. the latter the light is reflected towards the concave reflector so as to illuminate the image field 9. The entire set-up is. generally referred to as Schlieren-optical system or dark-field optics. If the control medium on concave reflector 1 is. smooth, light reflected by the concave mirror again impinges upon the. reflecting bars of system 2' and is thrown back to the light source. If, however, the surface of the medium is deformed in raster-like fashion as described below, the impinging light is defiected from its proper path. It may then pass by the bars of system 2 and reach the projection lens 3 and further the projection screen (not shown) over a deflection mirror 13. Lens 3 is arranged in such a manner that it projects an image of the rectangle 9 at the proje'ction screen. As the raster-shaped alterations of the control medium and consequently the amount of deflection of the light are proportional to the image signal the light flux produced by the light source 5 is controlled point by point in accordance with the image content and thus reconstitutes the televised image'on the projection screen.

Generally raster-shaped point-to-point deformation of the control medium is effected by electrical charges which are deposited on the surface of the control medium. by the cathode-ray. They cause corresponding deformations of the surface, i. e. a variation of the layer thickness. As the electron bombardment of the-scanning ray causes a certain fatigue of the control liquid, it is necessary to exchange continuously the control medium located within the image field. For this purpose the concave reflector is slowly rotated during operation in di: rection. of arrow 15 so that always new portions of the control medium pass under the cathode ray. The time interval in between two passages of a given spot of the control medium is, however, not long enough to permit the liquid to regenerate.

According to the present invention a fluid circuit driven by a pump is employed, which dispenses fresh liquid to the concave reflector through a slit-shaped nozzle in such a manner that the used liquid is removed and exchanged as completely as possible. The removed liquid is again fed to the. nozzle through a storage tank by the circuit.

As is shown in Fig. l a scavenging nozzle (or scavenging rake) 2t serve-s to exchange the liquid.

The nozzle is centered on shaft 22 by means of an eye 21. Two adjustable paws 23 serve to keep the nozzle at a given small distance from the mirror surface. By means of a pipe 24 liquid is fed to the nozzle by which the liquid adhering to the reflector is scavenged, as will be explained below with the aid of Fig. 2. The greater part of the scavenging liquid together with the removed liquid escapes from under the nozzle in direction opposite to the rotation 15 of the reflector. Through an opening 25 at the center of the reflector it reaches bowl 26 located therebelow. Accordin to representation the reflector is inclined so that a liquid sump 27 is formed on its lowest part wherein the scavenged liquid accumulates and again may flow to bowl 26 through opening 25. From bowl 26 the liquid flows to pump 28 and is fed back to the scavenging nozzle 22 by pipe 24 through a storage tank 29 thus completing the fluid circuit. As the entire device is located in vacuum it must be so designed that the liquid flows by natural gradient from the reflector to pump 28, or from the sump respectively, as aspiration of liquid by the pump is impossible with regard to the vacuum. The storage tank 29 must be made so large that the liquid stays therein a sufficient time permitting it to regenerate, i. e. to permit the above mentioned alterations caused by electron bombardment to reverse. Passage of the liquid through the tank must furthermore take place so slowly that no mixing of used and of regenerated liquid occurs. Due to the high viscosity of the liquid such mixture will practically never become homogeneous and will be incapable of effecting correct light control.

It may be mentioned that uniformity of light control action over the entire image field necessary for correct reproduction of the gradation of brightness requires that the layer thickness of non-deformed control medium be identical at all points of the image field 9. As furthermore the light control action essentially depends upon the viscosity of the control liquid, it is necessary to keep constant the temperature of the control medium.

Under certain circumstances a filter may be inserted into the fluid circuit in order to remove all disturbances (dust specks etc.) from the liquid. The presence thereof in the control liquid within the image field will produce disturbing phenomena on the projected image.

The scavenging nozzle 26) has a slit shaped opening 40 on its bottom surface extending radially over the reflector surface, which removes the liquid layer moved from the left towards the scavenging nozzle by rotation in opposite direction thereto. At the same time new liquid is applied to the reflector and is carried along to the right towards the image field 9. A smoothing rake 39 is located in between the scavenging nozzle 20 and the image field 9, whereby the correct thickness required for light control is given to the liquid layer produced by the scavenging nozzle. Separation of scavenging rake and smoothing rake proves advantageous as the thickness of the fluid layer escaping towards the right from under the scavenging rake depends upon the pressure with which the fluid is fed to the scavenging rake by the pump.

Fig. 2 shows a cross-section through the scavenging rake 20 and smoothing rake 30. The scavenging rake possesses a slit-shaped opening 4% which is oriented towards the surface of the concave reflector 41. To the concave reflector a reflecting layer 5.. is applied. The reflector is moved along under the scavenging rake in direction of arrow 43. The scavenging rake 20 has a cavity 44 to which fresh liquid is fed by pipe 24 with the necessary pressure. The greater partof the liquid escapes from the slit-shaped opening 45) in direction of arrow 4-6 and thus peels off the liquid layer 47 adhering to the reflector surface coming from the left, as it has been schematically shown in the drawing. The used, peeled-off liquid together with a scavenging liquid again returns into the liquid circuit as has been explained. above.

Part of the fresh fluid issues from the gap 49 formed between reflector surface and the front edge 48 of the scavenging rake. The slit nozzle consequently must be so designed that the greater part of the liquid issues towards the rear and removes the used liquid, whereas approximately only so much liquid passes through gap 49 as is required for forming the new control layer. By a smoothing rake 30 this control layer is brought to the correct thickness 50 required for projection, whereas the superfluous liquid held back by the smoothing rake accumulates within the space 51 between scavenging rake and smoothing rake and is likewise returned into the liquid circuit. The thickness of the liquid layer 50 may be adjusted at will within certain limits by displacing paws 23. In the drawing the paws simultaneously eflect adjustment of concave reflector and smoothing rake. Evidently separate adjustment may also be provided for. Under certain circumstances the functions of scavenging rake and smoothing rake may be united, if the fluid is fed by the pump with such uniformity that fluctuations of pressure and consequently fluctuations of layer thickness are positively eliminated.

It must be avoided that the liquid is permitted to pass by the sides of the scavenging rake, as that may give rise to disturbing effects. If by way of example in a device according to Fig. 1 liquid passes by the outer end of the rake on to the mirror edge a fluid ridge will form which flows slowly downward as the reflector rotates. This will impair the uniformity of layer thickness and furthermore an inhomogeneous mixture of used and new liquid will be produced. In order to avoid this, scavenging rake and smoothing rake may be made so long that they reach over the edge of the disc as is shown in Fig. 1. Fluid accumulating at the rear of the rake by the rotation of the reflector may then escape in outward direction. The liquid escaping outward is returned to the liquid circuit by suitable means.

The edge of the disc may alternatively be given the form schematically shown in Fig. 3, representing a section through the reflector along the rake. Rake 60 is centered on shaft 62 by eye 61. The concave reflector consists of a support plate 63 and a ground glass bowl 64 the surface of which is made reflecting. The fluid serving to form a control layer passes through the slit 65 between rake and reflector surface. In order to avoid formation of a fluid ridge a groove 66 is provided along the edge of the reflector bowl. This groove has sutficient size to accommodate the surplus of liquid passing by the edge so that formation of a fluid ridge is avoided. In certain cases the edge 67 of the disc may also be increased in height so that passing of the liquid by the side edge 68 of the rake is practically made impossible. The same effect may occur at the center of the reflector if the surplus of admitted fluid does not flow off through the opening at the reflector center. Support plate 63 and glass bowl 64 at the center provide a conical opening 70, the radius of which is larger than the radial distance between the axis of shaft 62 and the rake edge 71. Liquid passing between the shaft 62 and the rake edge 72 will then flow slowly down through opening 70. Formation of the disturbing fluid ridge at the reflector center is then avoided.

Under certain circumstances the liquid circuit according to the present invention may also be operated intermittently. This is possible if the employed control liquid has control properties only very little susceptible to the above mentioned effects. The apparatus may then be operated for a certain time without exchanging the control layer. In this case the fluid circuit is interrupted during projection so that no exchange of liquid is eflected on the reflector surface except perhaps exchange on a small scale within the sump located on the reflector surface. During the periods intervening between projection, the liquid adhering to the reflector is exchanged by means of the scavenging nozzle. For this purpose rotation of the minor and scavenging are continued until the layer of old liquid has been completely replaced by new regenerated liquid. After that the apparatus is again ready for projection.

The ratio of the amount of liquid located on the support and the total amount thereof circulating within the circuit, respectively, must be so chosen that regeneration is completed whilst the liquid passes through the storage tank. As has already been mentioned the liquid does not completely regenerate so that it is definitely exhausted after a certain number of cycles. It must then be replaced by new liquid. The total operation time after which this must take place will be the longer the larger the ratio of total liquid to the amount adhering to the support at a given moment, respectively.

What I claim is:

1. In television projection apparatus of the kind, wherein the light flux of a separate light source is controlled point by point with the aid of a thin layer of liquid adhering to the surface of a rotating support: a bowl into which liquid flows from said support, and means comprising a pump, a slit-shaped scavenging nozzle and a storage tank forming a fluid circuit for returning liquid to said support from said bowl, said pump feeding liquid from said tank to said nozzle and said nozzle dispensing said liquid so as to replace the used liquid layer on the support by a fresh liquid layer and said storage tank storing the used liquid thus removed from the support.

2. Television projection apparatus as claimed in claim 1, wherein the storage tank is given sufiicient size to ensure regeneration of the liquid during its passage.

3. Television projection apparatus as claimed in claim 1, wherein support is bowl-shaped with its axis inclined to the vertical, whereby used liquid removed by the scavenging nozzle accumulates and is returned into the fluid circuit.

4. In television projection apparatus of the kind, wherein the light fiux of a separate light source is controlled point by point with the aid of a thin layer of liquid adhering to the surface of a rotating support having a central opening through which liquid drains; the combination of a bowl for receiving liquid from said support, and scavenging means for stripping the liquid layer from said support and replacing it by a layer of fresh liquid, said scavenging means comprising a pump, a slit shaped scavenging nozzle and a storage tank, said pump feeding liquid from said bowl through said tank and to said nozzle, said scavenging nozzle having a slit on its bottom surface opposite the surface of said rotating support extending in approximately radial direction thereto to direct the greater part of the liquid fed to said nozzle in the direction opposite to the rotation of the support to remove the used liquid layer adhering thereto, which flows to said bowl for transfer by said pump to said storage tank, said scavenging nozzle including a smoothing edge for forming the liquid issuing in direction of rotation into a fresh liquid layer of desired thickness on said support.

5. Television projection apparatus as claimed in claim 4, wherein the scavenging nozzle includes means by which it is rotatably journalled at the center of the support and two adjustable paws slidably supporting said nozzle on the surface of the rotating support, said paws constituting means serving to adjust the thickness of the layer.

6. Television projection apparatus as claimed in claim 4, wherein the smoothing edge of the scanning nozzle reaches beyond the edge of the rotating support so that formation of a ridge of liquid is avoided.

7. Television projection apparatus as claimed in claim 4, wherein the smoothing edge of the scavenging nozzle reaches beyond said central opening of said rotating support so that formation of a ridge of liquid at the center is avoided.

References Cited in the file of this patent UNITED STATES PATENTS 2,391,451 Fischer Dec. 25, 1945 2,644,938 Hetzel et a1. July 7, 1953 2,668,130 Martin Feb. 2, 1954 2,668,796 Wehmiller et a1 Feb. 9, 1954 

